Wifi disconnects randomly - iOS 10.2.1

I have an iPhone 7 Plus that was with iOS 10.1.1 installed, everything working perfectly. But then I saw that iOS 10.2.1 was released, and whenever a "big" update is released (10.1 to 10.2), I restore through iTunes and set it up as new (without getting backup). From there I started my problem, in iOS 10.2.1, now the wifi disconnects randomly, and I can not even download a large file from the App Store (some games with more than 400 MB). What I tried to do:

I tried 2 different wifi networks (at home and at company). At home, it is working just fine, but at company, the problem persists. I have never had this problem in wifi's company!! Everything started when I updated to iOS 10.2.1....